Health

As al­ler­gies be­come more preva­lent, worms – or their lack – are be­ing blamed.

New Zealand Listener - - CONTENTS - By Nicky Pel­le­grino

As al­ler­gies be­come more preva­lent, worms – or their lack – are be­ing blamed.

Be­ing in­fected with in­testi­nal worms may not sound like an at­trac­tive propo­si­tion. Soon, how­ever, it may be the way we treat a range of al­ler­gies and auto­im­mune con­di­tions such as asthma, eczema and coeliac dis­ease. All are on the rise in de­vel­oped coun­tries, and the helminth, or par­a­sitic worm, is be­lieved to hold the key to why. “There is a the­ory called the ab­sent friends hy­poth­e­sis,” says Kara Fil­bey, a re­searcher at Welling­ton’s Malaghan In­sti­tute. “Our im­mune sys­tems evolved to have worms. We’re sup­posed to have some in­side us, but now we’ve erad­i­cated them com­pletely in the West­ern world.”

To make a home in­side the gut, worms need to be able to keep a lid on our im­mune sys­tem so it doesn’t at­tack them. With­out them there to con­trol the in­flam­ma­tory re­sponse, the the­ory is that our sys­tem starts re­spond­ing to things it shouldn’t, such as al­ler­gens in the en­vi­ron­ment.

“If you look at places where they do have worms en­dem­i­cally, such as Africa or South­east Asia, they have a lower rate of al­ler­gies and in­flam­ma­tory dis­ease,” says Fil­bey.

She has been do­ing helminth re­search for a decade and is a bit of a fan. “Worms are amaz­ing. They are big, mul­ti­cel­lu­lar or­gan­isms with their own mi­cro­biome and they have im­mune sys­tems them­selves, so they must be hav­ing a big ef­fect on us.”

Re­search is tak­ing place world­wide to dis­cover ex­actly what ef­fect par­a­sitic worms are hav­ing, and how that might be used to ben­e­fit our health. Fil­bey’s lat­est project has proved they are not merely ma­nip­u­lat­ing the

im­mune sys­tem.

She worked with mice, first giv­ing them a dose of a type of gut worm that nat­u­rally in­fects ro­dents in the wild. “That worm is in­duc­ing im­mune re­sponses, ob­vi­ously, as it’s a for­eign ob­ject, but you wouldn’t know the mouse had it,” she says. “Some of them ac­tu­ally look health­ier, with nice, shiny fur.”

Next, Fil­bey gave the same mice hook­worms, which en­ter through the skin and mi­grate via the lungs to the gut. A sur­pris­ing thing hap­pened. Rather than damp­en­ing the im­mune sys­tem, the orig­i­nal gut worm in­duced an im­mune re­sponse, ac­ti­vat­ing cells that cir­cu­late around the body and lodge in dif­fer­ent or­gans. The im­mune cells at­tacked and killed the hook­worm while it was still in the lungs.

So Fil­bey’s re­sults sug­gest that liv­ing with a “friendly par­a­site” could pro­tect hu­mans against in­fec­tion as well as au­toim­mune dis­eases.

There is still work to be done be­fore GPs can start pre­scrib­ing worms. The cor­rect dose of the right worm is vi­tal – a heavy bur­den can have dis­as­trous con­se­quences, stunt­ing growth or caus­ing anaemia, and is par­tic­u­larly harm­ful for chil­dren and preg­nant women.

We also need to come up with a more stream­lined way of pro­duc­ing helminths. At present, lar­vae for clin­i­cal tri­als are col­lected from the fae­ces of in­fected hu­man hosts, be­fore be­ing cleaned and given as a treat­ment.

Some peo­ple are not pre­pared to wait un­til worm ther­apy is main­stream. Des­per­ate for re­lief from a va­ri­ety of con­di­tions, in­clud­ing lu­pus and ir­ri­ta­ble bowel dis­ease, they are buy­ing worms on­line and self-in­fect­ing.

Ul­ti­mately, the aim is to pin­point ex­actly how worms are pro­tect­ing us. It may be they are se­cret­ing a mol­e­cule that can be de­liv­ered in the form of a pill or vac­cine. “But it may be the worm’s mi­cro­biome do­ing the job, not the ac­tual worm,” says Fil­bey. “We don’t know yet.”

Her lat­est work fo­cuses on how worm in­fec­tions can re­duce in­flam­ma­tory skin dis­eases such as der­mati­tis. So far, re­sults are look­ing good.

“Atopic der­mati­tis and eczema is the first al­ler­gic dis­ease you see early on in life. Peo­ple then go on to de­velop other al­ler­gic dis­eases such as hayfever, food al­lergy and asthma. This is called the al­ler­gic march.

“We think when your skin is dam­aged at that early stage, al­ler­gens are able to sen­si­tise your im­mune sys­tem and prime it to have an in­flam­ma­tory re­sponse later on when you in­gest that al­ler­gen or breathe it in. If we can tar­get der­mati­tis and that early skin bar­rier dys­func­tion, then maybe we could stop the whole al­ler­gic cas­cade through­out your life from hap­pen­ing.”

“Places that have worms en­dem­i­cally have a lower rate of al­ler­gies.”

Kara Fil­bey: gut worms can ward off hook­worms (above).

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